Methods for forming a barrier layer with periodic concentrations of elements and structures resulting therefrom

ABSTRACT

A method is provided which includes dispensing and removing different deposition solutions during an electroless deposition process to form different sub-films of a composite layer. Another method includes forming a film by an electroless deposition process and subsequently annealing the microelectronic topography to induce diffusion of an element within the film. Yet another method includes reiterating different mechanisms of deposition growth, namely interfacial electroless reduction and chemical adsorption, from a single deposition solution to form different sub-films of a composite layer. A microelectronic topography resulting from one or more of the methods includes a film formed in contact with a structure having a bulk concentration of a first element. The film has periodic successions of regions each comprising a region with a concentration of a second element greater than a set amount and a region with a concentration of the second element less than the set amount.

PRIORITY APPLICATION

The present application claims priority to provisional application no.60/599,975 entitled “Methods and Systems for Processing aMicroelectronic Topography” filed Aug. 9, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to methods for processing amicroelectronic topography and more particularly to electroless platingprocesses performed upon microelectronic topographies and structuresresulting therefrom.

2. Description of the Related Art

The following descriptions and examples are not admitted to be prior artby virtue of their inclusion within this section.

Electroless plating (also referred to herein as “electrolessdeposition”) is a process for depositing materials on a catalyticsurface from an electrolyte solution without an external source ofcurrent. An advantage of an electroless plating process is that it canbe selective, i.e., the material can be deposited only onto areas thatdemonstrate appropriate chemical properties. In particular, localdeposition can be performed onto metals that exhibit an affinity to thematerial being deposited or onto areas pretreated or pre-activated,e.g., with a catalyst. The ratio of the deposition rate on the activatedregions to the deposition rate at the non-activated regions is known asthe “deposition process selectivity.” For many applications, it isimportant to provide a deposition of high selectivity. For instance,high deposition selectivity may be advantageous for the formation ofmetal features within integrated circuits, such as but not limited tocontacts, vias, and interconnect lines.

Another important characteristic of an electroless plating process isproducing a deposition profile which is commensurate with thefabrication specifications of the device. For instance, in some cases,it may be advantageous to have a film deposited with substantiallyuniform thickness. In cases in which a film is electrolessly depositedacross a microelectronic topography, however, obtaining thicknessuniformity may be difficult. In particular, some electroless platingtechniques are susceptible to the “edge effect” in which portions of afilm deposited near the edge of the wafer are thinner than the portionsof the film deposited near the center of the wafer. Such an effect alsohinders fabrication specifications for depositing films having greaterthicknesses near the edge of the wafer as compared to near the center ofthe wafer.

As noted above, electroless plating may be used for the formation ofmetal features within integrated circuits. In some cases, electrolessplating techniques may be particularly favorable for depositingmaterials into deep and/or narrow holes that cannot be uniformly coveredby other deposition techniques, such as sputtering and evaporation, forexample. In addition, electroless plating techniques may be advantageousfor forming copper features, complementing the trend in the integratedcircuit industry of employing copper metallization structures instead ofaluminum, tungsten, silicides, or the like. In some microelectronicdevices, a barrier layer may be arranged beneath and/or upon a metalfeature to prevent elements within the metal feature from respectivelydiffusing to underlying and overlying layers of the topography. Suchbarrier layers may, in some embodiments, be formed by electrolessplating processes. Although conventional barrier layers are generallysufficient to inhibit most elemental diffusion from a metal feature,some diffusion may still occur. For example, copper atoms areparticularly notorious for being able to migrate through barrier layers.The migrated copper atoms can potentially be exposed to oxidation ormoisture at the surface of the barrier layer or may tunnel throughsilicon materials disposed adjacent to the barrier layer, affecting thereliability of the device and, in some cases, causing the device tomalfunction.

It would, therefore, be desirable to develop methods and systems forfabricating barrier layers which inhibit a greater degree of elementaldiffusion from overlying and/or underlying metal features than providedby conventional barrier layers. In addition, it would be beneficial todevelop systems and methods for electrolessly depositing films withoutincurring the edge effect.

SUMMARY OF THE INVENTION

The problems outlined above may be in large part addressed by methodsinvolving electroless plating processes for the formation of metalliclayers and structures within microelectronic topographies. The followingare mere exemplary embodiments of the methods and resulting structuresand are not to be construed in any way to limit the subject matter ofthe claims.

An embodiment of one of the methods includes positioning themicroelectronic topography within an electroless plating chamber,dispensing a first deposition solution upon the microelectronictopography to form a first sub-film, and subsequently removing the firstdeposition solution from the electroless plating chamber. The methodfurther includes dispensing a second deposition solution upon themicroelectronic topography subsequent to the removal of the firstdeposition solution to form a second sub-film upon and in contact withthe first sub-film. The second sub-film includes multiple elementsincluded within the first sub-film.

An embodiment of another of the methods includes forming a bulk metallicfilm upon the microelectronic topography using an electroless platingprocess. The bulk metallic film includes a bottom portion, a topportion, and an intermediate portion interposed between the bottom andtop portions. One of the top and bottom portions includes a higherconcentration of a first element than the intermediate portion and theother of the top and bottom portions. The method further includesannealing the microelectronic topography to induce diffusion of thefirst element within the bulk metallic film such that the intermediateportion comprises a higher concentration of the first element than thebottom and top portions.

An embodiment of yet another of the methods includes exposing amicroelectronic topography to a deposition solution and forming a firstsub-film portion by interfacial electroless reduction of a first elementwithin the deposition solution until a second different element reachesa certain concentration within the deposition solution. The firstsub-film includes a higher concentration of the first element than thesecond element. The method further includes forming a second sub-filmportion upon and in contact with the first sub-film portion by chemicaladsorption until the first element increases to a particularconcentration within the deposition solution. The second sub-filmincludes a higher concentration of the second element than the firstelement. In addition, the method includes reiterating the steps offorming the first and second sub-film portions to form a composite filmcomprising concentration variations of the first and second elements.

An embodiment of a microelectronic topography resulting from one or moreof the methods includes a structure having a bulk concentration of afirst element disposed throughout the structure and a film consistingessentially of one or more elements different than the first elementformed in contact with the structure. The film has periodic successionsof regions each comprising at least one region with a concentration of asecond element greater than a set amount and at least one region with aconcentration of the second element less than the set amount.

Another embodiment of a microelectronic topography resulting from one ormore of the methods includes a conductive structure having a bulkconcentration of copper disposed throughout the structure and a filmformed in contact with the conductive structure comprising alternatingregions of comparatively greater and lesser concentrations of cobalt.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to theaccompanying drawings in which:

FIG. 1 depicts a partial cross-sectional view of a microelectronictopography having a liner layer and cap layer formed about ametallization structure;

FIG. 2 a depicts an exemplary view of at least one of the liner layerand cap layer illustrated in FIG. 1, which may serve as a partialcross-sectional view or a partial plan view;

FIG. 2 b depicts another exemplary view of at least one of the linerlayer and cap layer illustrated in FIG. 1, which may serve as a partialcross-sectional view or a partial plan view;

FIG. 2 c depicts yet another exemplary view of at least one of the linerlayer and cap layer illustrated in FIG. 1, which may serve as a partialcross-sectional view or a partial plan view;

FIG. 3 depicts a flowchart of a method for forming a composite metalliclayer having a variation of elemental concentrations;

FIG. 4 depicts a flowchart of an alternative method for forming acomposite metallic layer having a variation of elemental concentrations;

FIG. 5 depicts a flowchart of another alternative method for forming acomposite metallic layer having a variation of elemental concentrations;

FIG. 6 depicts a flowchart of yet another alternative method for forminga composite metallic layer having a variation of elementalconcentrations;

FIG. 7 depicts a plan view of an electroless plating chamber configuredfor the method outlined in the flowchart of FIG. 6;

FIG. 8 depicts a schematic of a computer system which may be coupled toor incorporated within the electroless plating chamber illustrated inFIG. 8;

FIG. 9 depicts a plot of solution temperature versus process time for aplurality of different areas of a microelectronic topography;

FIG. 10 a depicts a partial cross-sectional view of a microelectronictopography having a film first deposited by a reaction limited mechanismof film growth and further deposited by a mass diffusion limitedmechanism of film growth;

FIG. 10 b depicts a partial cross-sectional view of a microelectronictopography having a film deposited exclusively by a reaction limitedmechanism of film growth;

FIG. 10 c depicts a partial cross-sectional view of a microelectronictopography having a film first deposited by a reaction limited mechanismof film growth, followed by a mass diffusion limited mechanism of filmgrowth, and finally by a second reaction limited mechanism of filmgrowth;

FIG. 11 depicts a plot of solution dispensing time versus a plurality ofdifferent areas of a microelectronic topography;

FIG. 12 depicts a flowchart of a method for depositing a film using anelectroless deposition chamber;

FIG. 13 depicts a cross-sectional view of an electroless plating chamberconfigured for the method outlined in the flowchart of FIG. 12;

FIG. 14 depicts a plan view of an exemplary test wafer having distinctregions each including comparatively different thicknesses andcomparatively different elemental concentrations;

FIG. 15 a depicts a partial cross-sectional view of the test waferillustrated in FIG. 14; and

FIG. 15 b depicts an alternative partial cross-sectional view of thetest wafer illustrated in FIG. 14.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detaileddescription thereto are not intended to limit the invention to theparticular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the present invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning to the drawings, exemplary methods and systems involvingelectroless plating processes for the formation of metallic layers andstructures within microelectronic topographies are shown. In addition,microelectronic topographies resulting from the use of such methods andsystems are shown. For instance, FIG. 1 illustrates a partialcross-sectional view of microelectronic topography 20 having liner layer28, cap layer 30, as well as other metallic structures which may beformed from the methods and systems described below in reference toFIGS. 3-13. Although the methods and systems described below arespecifically discussed in reference to the formation of barrier layersand, therefore, are specific to liner layer 28 and cap layer 30, any ofthe metallic structures of microelectronic topography 20, includingthose formed below lower layer 26 and those formed above cap layer 30,may be formed by the methods and systems described below in reference toFIGS. 3-13.

As will be described in more detail below, the elemental composition ofliner layer 28 and cap layer 30 may be configured to reduce thediffusion of elements from metallization structure 22 to lower layer 26,dielectric layer 24 and any layers formed upon cap layer 30, reducingelectromigration within an ensuing device. In addition, cap layer 30 maybe configured to prevent oxidation of metallization structure 22. Assuch, liner layer 28 and cap layer 30 may generally be referred to asbarrier layers. Such a reference, however, does not necessarily inferthe exclusivity of the aforementioned functions. In particular, linerlayer 28 and/or cap layer may additionally or alternatively serve asadhesion layers and/or thermal expansion buffers. Exemplary elementalcompositions of liner layer 28 and/or cap layer 30 resulting from theuse of the methods and/or systems described in reference to FIGS. 3-13are shown in FIGS. 2 a-2 c and are discussed in more detail below. It isnoted that microelectronic topography 20 is not necessarily limited tohaving both liner layer 28 and cap layer 30 be formed by the methods andsystems described herein. In particular, the methods and systems may beapplied to either or both of such layers. In addition, althoughmicroelectronic topography 20 is shown including both liner layer 28 andcap layer 30, the topography is not necessarily so limited. Inparticular, microelectronic topography 20 may alternatively include onlyone of liner layer 28 and cap layer 30.

In general, the term “microelectronic topography” may refer to asubstrate resulting from or used for the fabrication of amicroelectronic device or circuit, such as an integrated circuit, forexample. As such, metallization structure 22 may be any metal featureknown for the fabrication of a microelectronic device. For example,metallization structure 22 may, in some embodiments, serve as a contactstructure to portions of a semiconductor layer. In such cases, lowerlayer 26 may include a semiconductor material, such as silicon and may,in some embodiments, be doped either n-type or p-type. Morespecifically, lower layer 26 may be a monocrystalline silicon substrateor an epitaxial silicon layer grown on a monocrystalline siliconsubstrate. In addition or alternatively, lower layer 26 may include asilicon on insulator (SOI) layer, which may be formed upon a siliconwafer. In other cases, lower layer 26 may include metallization and/oran interlevel dielectric layer. In such embodiments, metallizationstructure 22 may serve as a via, an interconnect or any othermetallization feature to underlying portions of microelectronictopography 20.

In any case, metallization structure 22 may include one or more layersof conductive materials, including but not limited to copper, aluminum,tungsten, titanium, silver, or any alloy of such metals. In someembodiments, the methods and systems described herein may beparticularly applicable to microelectronic topographies including ametallization structure having a bulk concentration of copper and, insome cases, consisting essentially of copper. In particular, copper hasa relatively low resistivity and, therefore, is often favorable to usefor metallization structures in microelectronic devices. As noted above,copper atoms are particularly notorious for their propensity to diffusethrough materials. The methods and systems described herein, however,offer manners in which to fabricate barrier layers around coppermetallization structures to substantially minimize or eliminate thediffusion of copper to other layers.

In some embodiments, metallization structure 22 may, in someembodiments, be fabricated by electroless plating techniques, includingthose described herein as well as others known in the microelectronicfabrication industry. In other embodiments, metallization structure 22may be formed by other deposition techniques known in themicroelectronic fabrication industry, such as but not limited tosputtering or evaporation. In either case, metallization structure 22may be formed within a trench formed within dielectric layer 24. Such afabrication sequence may be particularly advantageous for theincorporation of liner layer 22 within microelectronic topography 20. Inother embodiments, dielectric layer 24 may be formed subsequent to andabout metallization structure 22.

Dielectric layer 24 may include one or more of various dielectricmaterials used in microelectronic fabrication. For example, dielectriclayer 24 may include silicon dioxide (SiO₂), silicon nitride(Si_(x)N_(y)), silicon dioxide/silicon nitride/silicon dioxide (ONO),silicon carbide, carbon-doped SiO₂, or carbonated polymers. In somecases, dielectric layer 24 may be undoped. Alternatively, dielectriclayer 24 may be doped to form, for example, low doped borophosphorussilicate glass (BPSG), low doped phosphorus silicate glass (PSG), orfluorinated silicate glass (FSG). In some embodiments, dielectric layer24 may be formed from a low-permittivity (“low-k”) dielectric, generallyknown in the art as a dielectric having a dielectric constant of lessthan about 3.5. One low-k dielectric in current use, which is believedto make a conformal film, is fluorine-doped silicon dioxide. In anycase, dielectric layer 24 may have a thickness between approximately2,000 angstroms and approximately 10,000 angstroms. Larger or smallerthicknesses of dielectric layer 24, however, may be appropriatedepending on the microelectronic device being formed.

As noted above, the elemental composition of liner layer 28 and caplayer 30 may be configured to reduce the diffusion of elements frommetallization structure 22. As such, the selection and arrangement ofthe elements included within liner layer 28 and cap layer 30 may, insome embodiments, depend on the elements included in metallizationstructure 22. In embodiments in which metallization structure 22includes copper, the inclusion of cobalt within liner layer 28 and caplayer 30 may be particularly beneficial since copper has relatively lowsolubility with cobalt. Other materials which may be additionally oralternatively included within liner layer 28 and cap layer 30 mayinclude phosphorus, boron, tungsten, chromium, molybdenum, nickel,palladium, rhodium, ruthenium, oxygen, and hydrogen.

Exemplary alloys which may be employed for liner layer 28 and cap layer30 include but are not limited to cobalt-tungsten-phosphorus (CoWP),cobalt-tungsten-boron (CoWB), cobalt-tungsten-phosphorus-boron (CoWPB),cobalt-molybdenum-boron (CoMoB), cobalt-molybdenum-phosphorus (CoMoP),cobalt-molybdenum-chromium (CoMoCr), andcobalt-molybdenum-chromium-boron (CoMoCrB). In other embodiments, linerlayer 29 and/or cap layer 30 may include single element layers ofpalladium, rhodium and ruthenium. It is noted that although hydrogen isnot listed as an element with such exemplary materials, it may beincorporated therein as a result of the electroless plating process asdescribed in more detail below. In some embodiments, liner layer 29 andcap layer 30 may include the same collection of elements and, in somecases, a similar arrangement of elements. In other cases, however, linerlayer 29 and cap layer 30 may include different arrangements of elementsand, in some embodiments, a different collection of elements.

In some embodiments, liner layer 28 and/or cap layer 30 may include avariation of elemental concentrations throughout the layers to reducethe diffusion of elements from metallization structure 22 therethrough.In particular, liner layer 28 and/or cap layer 30 may include differentconcentrations of elements in different regions of the layer. Exemplaryelemental compositions of liner layer 28 and/or cap layer 30 are shownin FIGS. 2 a-2 c. In some cases, the variation of elements within linerlayer 28 and cap layer 30 may be arranged in sub-layers verticallydisposed within the films. As such, FIGS. 2 a-2 c may, in someembodiments, illustrate partial cross-sectional views of liner layer 28and/or cap layer 30. In other cases, the variation of elements may beadditionally or alternatively arranged in regions extending horizontallybetween lateral edges of the films. As such, FIGS. 2 a-2 c mayalternatively illustrate partial plan views of the upper surface of caplayer 30. In such embodiments, liner layer 28 may, in some cases,include a similar horizontal variation of elements and, therefore, FIGS.2 a-2 c may apply to liner layer 28 for horizontal variations ofelements as well. In some cases, the variation of element concentrationsmay vary both horizontally and vertically within the films and,therefore, FIGS. 2 a-2 c may be representative of either across-sectional view or a plan view of the layers.

As shown in FIG. 2 a, liner layer 28 and/or cap layer 30 may, in someembodiments, include alternating regions of comparatively greater andlesser concentrations of an element. More specifically, FIG. 2 aillustrates an arrangement of atoms of an element (each atom shown as an“x” in FIG. 2 a) which, in an effect, partitions the layer into regions32 comprising comparatively fewer atoms of the element and regions 34comprising comparatively greater quantities of atoms of the element.Regions 32 and 34 are disposed along opposing sides of each other and,therefore, alternative through the film. Regions 32 and regions 34 maybe differentiated from each other by including concentrations of anelement which respectively fit into different ranges of concentrations.For example, in some embodiments, regions 32 may include betweenapproximately 30% and approximately 50% of an element, while regions 34may include between approximately 5% and approximately 20% of anelement. Larger or smaller ranges and magnitudes of elementalconcentrations may be employed depending on the element of differingconcentration and the design specifications of the device. Consequently,the barrier films disclosed herein are not necessarily limited to theaforementioned values. Since regions 32 and regions 34 aredifferentiated by different ranges of elemental concentrations, neitherregions 32 nor regions 34 need to necessarily include the sameconcentrations of an element as shown in FIG. 2 a. Noting such a scopeof the film, the elemental concentrations of regions 32 and 34 are notnecessarily restricted to having different elemental concentrationseither. Therefore, in some cases, two or more of the respective regionsmay include the same elemental concentration.

It is noted that elemental atoms other than the one shown in FIG. 2 amay be included within liner layer 28 and cap layer 30. In addition,although FIG. 2 aillustrates variation of only a single element withinliner layer 28 and cap layer 30, other elements within the film mayvary. In some embodiments, the other elements may vary in a similarmanner as element x and, therefore, may be disposed within regions 34and 32 having comparatively greater and lesser concentrations,respectively. In other embodiments, regions 32 and 34 may include anopposite arrangement of greater and lesser concentrations of the one ormore elements. In particular, regions 32 may include a low concentrationof element x and a high concentration of another element and vice versafor regions 34. In yet other embodiments, the concentration variation ofthe other element may not alternate through the film, but may follow itsown succession of regions having varying concentrations of the element.In any case, regions 32 and 34 are not restricted to having the sameconcentration levels of different elemental atoms. In particular,regions 32 and 34 may include different ranges of concentrations foreach element. Alternatively, the concentration of other elements may notsubstantially vary through the film.

An alternative arrangement of elements for liner layer 28 and cap layer30 is illustrated in FIG. 2 b. In particular, FIG. 2 b illustrates linerlayer 28 and cap layer 30 having concentration variations of twodifferent elements (atoms of the elements shown as “x” and “o”). Asshown in FIG. 2 b, the relative concentrations of the elements do notalternate through the films, but rather are disposed as periodicsuccessions of regions 36. More specifically, periodic successions ofregions 36 are shown having three regions with relatively differentconcentrations of element atoms “x” and “o.” Although periodicsuccessions of regions 36 are shown to include three regions, linerlayer 28 and cap layer 30 are not necessarily so restricted. Inparticular, periodic successions of regions 36 may include any pluralityof regions.

Each of periodic successions of regions 36 includes at least one regionwith a concentration of an element greater than a set amount and atleast one region with a concentration of the element less than the setamount. The set amounts may generally depend on the individual elementand the design specifications of the film and, therefore, may varybetween approximately 1% and approximately 99%. Set amounts for themultiple elements within a film are generally independent of each other.As shown in FIG. 2 b, periodic successions of regions 36 may includeregion 36 a having a greater concentration of elemental atoms “x” and“o” than region 36 b, which includes a greater concentration than region36 c. In such cases, region 36 a may include a concentration ofelemental atoms “x” and “o” greater than a set amount and region 36 cmay include a concentration of elemental atoms “x” and “o” less than theset amount. Region 36 b may fit into either of such categories,depending on the design specifications of the film. As such, periodicsuccessions of regions 36 may include a series of regions havingincrementally increasing relative concentrations. In other embodiments,regions 36 a, 36 b, and 36 may be arranged in an alternative sequence,such as having regions 36 a or 36 c interposed between the other regionssuch that progression of elemental concentrations through periodicsuccessions of regions 36 is not incremental.

In any case, periodic successions of regions 36 may include regionswhich are differentiated from each other by respectively differentranges of elemental concentrations. As such, each of regions 36 a (aswell as each of regions 36 b and 36 c) do not necessarily need toinclude the same concentrations of elemental atoms “x” or “o.”Furthermore, periodic successions of regions 36 are not restricted tohaving the same concentration levels of element atoms “x” and “o.” Inparticular, regions 36 a, 36 b and 36 c may include different ranges ofconcentrations for each element. Moreover, the relative level ofelemental concentrations among regions 36 a, 36 b, and 36 c may bedifferent for each of the elements respectively associated with atoms“x” and “o.” For example, region 36 a may alternatively include therelatively highest amount of elemental atoms “x” and include therelatively lowest amount of elemental atoms “o” among each succession ofregions 36. In other embodiments, region 36 b or 36 c may alternativelyinclude the relatively highest amount of elemental atoms “x” and therelatively lowest amount of elemental atoms “o” among each succession ofregions 36.

Another alternative composition of elements for liner layer 28 and/orcap layer 30 is illustrated in FIG. 2 c. In particular, FIG. 2 cillustrates liner layer 28 and/or cap layer 30 including region 38 witha relatively high concentration of element “+” interposed betweenregions 39 having comparatively lower concentrations of the element. Asdescribed in more detail below, such an arrangement may be resultant ofthe method described below in reference to FIG. 4, although it is notnecessarily limited to such a method of formation. As with regions 32and 34 of FIG. 2 a, regions 39 do not necessarily need to include thesame concentration of element “+.” Rather, regions 39 may includeconcentrations of an element which fits into a different range ofconcentrations than the concentration of region 38. In addition, region38 is not restricted to being centered within liner layer 28 and caplayer 30.

It is noted that liner layer 28 and cap layer 30 are not necessarilyrestricted to the configurations illustrated in FIGS. 2 a-2 c. Inparticular, liner layer 28 and cap layer 30 may include any variation ofelemental concentrations among distinct regions of the films. In someembodiments, it may be particularly advantageous for at least one ofliner layer 28 and cap layer 30 to include a periodic arrangement ofconcentration levels in order to inhibit diffusion from metallizationstructure 22. In particular, liner layer 28 and/or cap layer 30 mayinclude different concentrations of one or more elements at regularintervals of the layer as shown in FIGS. 2 a and 2 b, for example. Inother embodiments, the variation of elemental concentration shown inFIG. 2 c may be appropriate to inhibit diffusion from metallizationstructure 22.

In general, the elements which are configured to vary within liner layer28 and/or cap layer 30 may be any of the elements which may be includedwithin the films. In particular, the elements having varyingconcentrations in liner layer 28 and cap layer 30 may be cobalt,phosphorus, boron, tungsten, chromium, molybdenum, nickel, palladium,rhodium, ruthenium and/or hydrogen. As noted above, copper hasrelatively low solubility with cobalt and, therefore, it may beadvantageous to vary the concentration of cobalt within liner layer 28and/or cap layer 30 in some embodiments. In particular, a variation ofcobalt concentration throughout liner layer 28 and cap layer 30 maysubstantially reduce the migration of copper through the films comparedto embodiments in which the concentration of cobalt is substantiallyeven. In turn, the likelihood of copper atoms reaching surroundinglayers may be reduced. In some cases, the level of cobalt concentrationmay alternate through liner layer 28 and cap layer 30. Consequently, insome cases, liner layer 28 and cap layer 30 may include a composite filmof alternating cobalt-rich and cobalt-poor regions.

In any case, it may be further advantageous to include a relatively highconcentration of cobalt in regions of liner layer 28 and/or cap layer 30directly adjacent and in contact with metallization structure 22 toimprove the adhesion to the copper material. Such an arrangement,however, is not necessarily required and, therefore, microelectronictopography 20 is not intended to be restricted to such a configuration.As noted above, liner layer 28 and cap layer 30 may include periodicregions of different concentrations of other elements as well oralternatively. It is noted that the variation of symbols denotingdifferent elemental atoms in FIGS. 2 a-2 c (i.e., “x,” “o,” and “+”) donot necessarily imply that the different configurations are particularto specific elements or combinations of elements. The differentiation ismerely shown to emphasize that different elements may be formed in aperiodic manner within barrier layers.

Although variations of elemental concentrations within liner layer 28and cap layer 30 may differ depending on the design specifications ofmicroelectronic topography 20, some exemplary ranges may be applicableto many applications. For instance, an exemplary cobalt concentrationvariation may be between, for example, approximately 10% andapproximately 30%, or more specifically, a variation of approximately20%. In addition, an exemplary variation of phosphorus concentration maybe between approximately 3% and approximately 12% and a variation ofboron concentration may be between approximately 1% and approximately2%. In some cases, liner layer 28 and cap layer 30 may include aconcentration variation of molybdenum between approximately 1% andapproximately 50%. Larger or smaller variations of concentrations may beemployed for any of such elements as well as the other elements listedfor liner layer 28 and cap layer 30 and, therefore, the aforementionedlimitations do not necessarily limit the range of elementalconcentrations within the layers.

Several methods are described herein for forming a barrier layer (suchas liner layer 28 and/or cap layer 30) with a variation of thecomponents. For example, one method for forming a barrier layer with avertical variation of elemental concentrations may include depositing aplurality of sub-layers having different concentrations of elements. Aflowchart of a method of depositing a plurality of sub-layers havingdifferent concentrations of elements is shown in FIG. 3. As shown inblocks 40 and 42 of FIG. 3, the method may include positioning amicroelectronic topography within an electroless plating chamber anddispensing a first deposition solution upon the microelectronictopography to form a first sub-layer upon the microelectronictopography. In some embodiments, the process may further includerotating a substrate holder upon which the microelectronic topography ispositioned to facilitate the distribution of the first depositionsolution across the topography. The first sub-layer may include one ormore elements formed within individual concentration ranges.

In some embodiments, the distribution of the first deposition solutionmay be a single continuous flow across the surface of microelectronictopography. In other embodiments, the distribution of the firstdeposition solution may be a series of fragmented depositions of thesolution at different locations extending different distances from acenter of the microelectronic topography. Such a technique may induce ahorizontal variation of element concentrations within the firstsub-layer and, in some cases, subsequent sub-films. Consequently, theensuing composite layer may include both vertical and horizontalvariations of elemental concentrations. An exemplary method and systemfor dispensing deposition solution in a series of fragmented times andlocations are described in more detail below in reference to FIGS. 6-8.In some cases, the method may additionally or alternatively be performedin a chamber configured to induce a variation of evaporation ratesacross a topography such that a horizontal variation of elementalconcentrations within the first and/or subsequent sub-films may beobtained by such a manner. An exemplary method and system for varyingevaporation rates across a microelectronic topography during anelectroless deposition chamber are described in more detail below inreference to FIGS. 12 and 13.

In any case, the method may, in some embodiments, include blocks 43 aand 43 b in which dispensing the deposition solution and/or rotation ofthe substrate holder (when so applied) is terminated and subsequentlyresumed during the deposition of the first sub-film. In someembodiments, the processes associated with blocks 43 a and 43 b may beconducted as a single sequence of steps as indicated by the singledirection arrow between the blocks. In other cases, the processesassociated with blocks 43 a and 43 b may be reiterated multiple timesduring the deposition process as indicted by the bi-directional arrowbetween the blocks. In such embodiments, the sequence of steps may endwith either of the processes when the method continues onto block 44even though FIG. 1 illustrates the method continuing on to block 44 fromblock 43 b. In either case, the sequence of steps may advantageouslyfacilitate a substantial uniform deposition of elemental componentsacross the topography within the first sub-film while still preventingthe accumulation of bubbles upon the topography during deposition, asdescribed in more detail below. The sequence of steps may additionallyor alternatively be used during the deposition of subsequent sub-filmsas well. As such, although the overall method described in reference toFIG. 3 is used to fabricate a composite barrier layer with a variationof elemental concentrations (i.e., among the different sub-films), thesub-film layers themselves may be formed to have a substantially uniformdistribution and concentration of elements.

It is theorized that the adsorption potential of charged moleculeswithin a deposition solution is influenced by the ratio of differentsurface materials (e.g., amount of conductive surfaces versus dielectricsurfaces) within a given area of a topography. In particular, it istheorized that an area with a greater density of conductive structures(i.e., an area with relatively less dielectric surface material) mayhave a stronger affinity for adsorbing charged molecules than an area ofrelatively lower density of conductive structures. As a result, the areawith the greater density of conductive structures may have a differentconcentration and distribution of elements than the area with the lesserdensity of conductive structures. It has been discovered, in conjunctionwith the development of the methods described herein, that thetermination of dispensing the deposition solution and/or the terminationof rotating the substrate holder during the deposition of a film mayreduce or negate variations of charged molecule adsorption potentialsrelative to areas of a topography having different densities of surfacematerials. In particular, it has been found that the termination of oneor more of the processes associated with block 43 a allows films havingsubstantially similar distribution and concentration of elements to bedeposited across a topography.

In some cases, however, the termination processes of block 43 a maycause the formation of bubbles upon the microelectronic topography. Theformation of bubbles during electroless deposition processes often causeundesirable random non-uniformity in deposition thickness and, in somecases, cause defects to be formed within the film. The recommencement ofdispensing the deposition solution and/or rotating the substrate holderas noted in block 43 b, however, may advantageously remove bubblesformed from the termination processes. As a result, a film having asubstantially uniform elemental composition, uniform thickness, aminimal number or no defects may be deposited with the techniquedescribed herein.

In general, the duration of termination and resumption of the processesdescribed in reference to FIG. 43 a and 43 b may be betweenapproximately 0.5 seconds and approximately 1 minute. Shorter or longerdurations, however, may be employed for each of such processes. In someembodiments, it may be advantageous for the termination of the processesto be short, such as between approximately 0.5 seconds and approximately5 seconds, or more specifically about 2 seconds, to reduce the formationof bubbles during the deposition process. In some cases, it may bebeneficial for the termination of the processes to be shorter than theduration for which the processes are resumed. For example, in someembodiments, it may be advantageous to resume the processes for aduration between approximately 15 seconds and approximately 45 seconds,or more specifically about 30 seconds. In other cases, however, theduration of the processes may be the same or the termination of theprocesses may be longer than the duration for resuming the processes. Inyet other embodiments, blocks 43 a and 43 b and the associatedtermination and resuming processes may be omitted from the methoddescribed in reference to FIG. 3. Blocks 43 a and 43 b and the arrowsextending to and from it are outlined with dotted lines indicating thesteps are optional.

In any case, the method may continue by removing the first depositionsolution from the electroless plating chamber and subsequentlydispensing a second deposition solution upon the microelectronictopography to form second sub-layer upon and in contact with the firstsub-layer as respectively noted by blocks 44 and 48 in FIG. 3. As withthe formation of the first sub-layer, the disbursement of the seconddeposition solution may be a single continuous flow or may be a seriesof fragmented depositions. In addition, the method may, in someembodiments, continue to blocks 43 a and 43 b such that the depositionof the second sub-film includes the termination of dispensing thedeposition solution and/or the termination of rotating the substrateholder as similarly described above for the formation of the firstsub-film.

In any case, the second sub-layer may include multiple elements whichare also included within the first sub-layer. In some embodiments, thesecond sub-layer may consist essentially of the same elements asincluded in the first sub-layer. In other embodiments, however, thefirst and second sub-layer may include some different elements. In anycase, the second sub-layer may include one or more elements havingconcentrations within different ranges than employed within the firstsub-layer. In other words, a concentration of at least one of theelements within the second sub-layer may differ from a concentration ofthe same element within the first sub-layer. In this manner, the methodinduces a vertical variation of elemental concentrations.

As shown in FIG. 3, the method may, in some embodiments, include block46 in which chamber process parameters different than those used for theformation of the previous sub-film are established. The incorporation ofblock 46 prior to the formation of the second sub-layer, as shown inFIG. 3, may in turn include establishing chamber process parametersdifferent than those used during the formation of the first sub-layer.Such different process parameters may be wholly or partially responsiblefor the variations of elemental concentrations between the first andsecond sub-layers. In particular, the change in parameters by which theelectroless deposition process is conducted may be sufficient to affectthe concentration of elements within the second sub-layer as compared tothe first sub-layer. Such influential process parameters may include butare not limited to temperature, pressure, and the type of ambient gasincluded within the electroless plating chamber.

In some embodiments, the first and second depositions solutions mayinclude the same compositions and, therefore, the changes of chamberprocess parameters may be wholly responsible for the variations ofelemental concentrations between the first and second sub-layers. Inother embodiments, the first and second depositions solutions mayinclude different compositions and, therefore, the changes of chamberprocess parameters may be partially responsible for the variations ofelemental concentrations between the first and second sub-layers. In yetother embodiments, block 46 may not be employed prior to the formationof the second sub-layer. In such cases, the variation of compositionsamong the first and second deposition solutions may be whollyresponsible for the variation of elemental concentrations between thefirst and second sub-layers. Block 46 and the arrows extending to andfrom it are outlined with dotted lines indicating the step is optionaland, therefore, block 46 and the associated establishment of differentchamber process parameters may be omitted in some cases.

Regardless of whether different chamber process parameters areestablished prior to the formation of the second sub-layer, the seconddeposition solution may be removed from the electroless plating chambersubsequent to the formation of the second sub-layer as shown by block 50in FIG. 3. Thereafter, the method may follow several different routes.In particular, the method may, in some embodiments, end at block 58after the removal of the second deposition solution from the electrolessplating chamber. Alternatively, the method may include repeating thesteps of dispensing and removing the first deposition solution(described in reference to block 42 and 44 ) to form a third sub-layerupon and in contact with the second sub-layer as shown by block 52 inFIG. 3. As with the second sub-layer, the third sub-layer may include amultiple of the same elements included within the first sub-layer. Inaddition, the method may, in some embodiments, continue to blocks 43 aand 43 b such that the deposition of the third sub-film includes thetermination of dispensing the deposition solution and/or the terminationof rotating the substrate holder as similarly described above for theformation of the first sub-film.

In some cases, the third sub-layer may consist essentially of the sameelements as included in the first sub-layer. In other embodiments,however, the first and third sub-layers may include some differentelements. In either case, the third sub-layer may, in some embodiments,include a concentration of at least one element which is closer to aconcentration of the same element with the first sub-layer than aconcentration of the same element within the second sub-layer. Inparticular, the third sub-layer may include one or more elements havingconcentrations within the same ranges as employed within the firstsub-layer. In this manner, the method may induce a periodic variation ofan element concentration similar to but not limited to theconfigurations described in reference to FIGS. 2 a and 2 c. In otherembodiments, the third sub-layer may include a substantially differentconcentration of an element included within the first and secondsub-layers and, therefore, may be similar to the configuration describedin reference to FIG. 2 b.

Following an alternative route, the method may include reiterating thesteps of dispensing and removing the first deposition solution(described in reference to block 42 and 44) and the steps of dispensingand removing the second deposition solution (described in reference toblock 48 and 50) to form additional sub-layers above the secondsub-layer as shown in block 54 of FIG. 3. In addition or alternatively,the method may include consecutively dispensing and removing one or moreadditional deposition solutions different than the first and seconddeposition solutions to form one or more additional sub-layers above thesecond sub-layer as noted in block 56. In either case, the additionalfilms may be configured to induce a periodic variation of an elementalconcentration with the first and second sub-films similar to but notlimited to the configurations described in reference to FIGS. 2 a-2 c.

In addition, the processes embodied by blocks 54 and 56 may be repeatedany number of times to form the composite barrier layer. For example,the processes may be repeated to form up to approximately 100 sub-filmlayers. In some embodiments, a composite barrier layer of less than fivesub-films may be advantageous to minimize the thickness of the ensuingbarrier layer, but is not necessarily limited for such reasons. Thethickness of each sub-film formed by the method described in FIG. 3 maybe between approximately 0.5 nm and approximately 100 nm, or morespecifically between approximately 0.5 nm and approximately 50 nm.Sub-films with larger or smaller thicknesses, however, may be used toform the composite barrier layer described herein. It is noted that themethod may, in some embodiments, continue to blocks 43 a and 43 b forany number of the sub-films formed by blocks 54 and 56 and, therefore,the deposition of such sub-films may, in some embodiments, include thetermination of dispensing the deposition solution and/or the terminationof rotating the substrate holder as similarly described above for theformation of the first sub-film.

As shown by the dotted lines to block 46 after the progression of stepsthrough block 50 in FIG. 3, the method may sometimes includeestablishing chamber process parameters different than those used forthe formation of the previous sub-layer after the removal of the seconddeposition solution. In particular, FIG. 3 shows that the method may, insome embodiments, include block 46 subsequent to block 50 and prior toany of blocks 52, 54, 56 or 58. The incorporation of block 46 subsequentto the formation of the second sub-layer thus may include establishingchamber process parameters different than those used during theformation of the second sub-layer. In some embodiments, the chamberprocess parameters may further be different from the chamber processparameters used during the formation of the first sub-layer. In suchcases, the sub-layer formed upon the second sub-layer may includedifferent elemental concentrations than the first and second sub-layers.In yet other embodiments, the chamber process parameters may besubstantially similar to the parameters used during the formation of thefirst sub-layer such that a composite barrier layer having alternatingregions of comparatively greater and lesser concentrations of one ormore elements may be formed.

As with the optional modification of chamber process parameters prior tothe formation of the second sub-layer discussed above, the change ofprocess parameters prior to the formation of additional sub-layers abovethe second sub-layer may be wholly or partially responsible for thevariations of elemental concentrations between the additional sub-layersand the second sub-layer. As such, deposition solutions dispensed uponthe microelectronic topography subsequent to the removal of the seconddeposition solution may include the same or different elementalcompositions as the first and second deposition solutions. It is furthernoted that block 46 may be incorporated into the method directly priorto one or more of the individual additional sub-films referenced withrespect to blocks 54 and 56. Reference arrows indicating suchpossibilities have been omitted from FIG. 3 to simplify the drawing.

In general, the process parameters for the deposition of the sub-filmswith respect to the method depicted in FIG. 3 (as well as the othermethods described herein) may depend on the design specifications of thesub-films, such as but not limited to their elemental compositions andthicknesses, for example. Some exemplary process parameters, however,may include deposition solution flows between approximately 0.5 L/minand approximately 10 L/min and, in some embodiments, approximately 2L/min. In addition, wafer rotating speeds during deposition may bebetween approximately 1 rpm and approximately 100 rpm and, in someembodiments, approximately 30 rpm. In some embodiments, wafer rotationspeeds during the removal of the deposition solutions may be faster,such as between approximately 150 rpm and approximately 2000 rpm and, insome cases, approximately 300 rpm. In this manner, the processing timebetween deposition cycles may be minimized. For example, in someembodiments, the processing time between deposition cycles may beapproximately 5 seconds. The process time to deposit the sub-films, onthe other hand, may be between approximately 10 seconds and a fewminutes, and more specifically, between approximately 10 seconds andapproximately 30 seconds. Furthermore, the temperature at which theelectroless deposition process occurs may be between approximately 20°C. and approximately 120° C., or more specifically, betweenapproximately 55° C. and approximately 90° C. In general, larger orsmaller temperatures and slower and/or faster deposition flows, waferrotation speeds, and process cycles times may be used to form thecomposite barrier layer and, therefore, the methods described herein arenot necessarily limited to the aforementioned values.

Tables 1 and 2 below outline exemplary compositions of depositionsolutions and chamber process parameters associated with the methodsdescribed herein, particularly in reference to FIG. 3 but notnecessarily so limited. In particular, Tables 1 and 2 outline exemplarycompositions of deposition solutions and chamber process parameters fordepositing sub-films of a composite barrier layer with a verticalvariation, and in some embodiments a horizontal variation, of elementalconcentrations. More specifically, Table 1 displays exemplarycompositions of deposition solutions and chamber process parameters usedto form sub-films of cobalt-tungsten-phosphorus (CoWP),cobalt-tungsten-phosphorus-boron (CoWPB), cobalt-molybdenum-phosphorus(CoMoP), cobalt-molybdenum-phosphorus (CoMoP), andcobalt-molybdenum-chromium-boron (CoMoCrB). Table 2, on the other hand,displays exemplary compositions of deposition solutions and chamberprocess parameters used to form sub-films of some of such cobalt alloyswith relatively high concentrations of W and Mo, such as greater thanapproximately 25%, for example. Table 2 also displays exemplarycompositions of deposition solutions and process parameters used to formruthenium (Ru) sub-films. TABLE 1 Exemplary Compositions of DepositionSolutions and Chamber Process Parameters used to form Films of CoWP,CoWPB, CoWB, CoMoB and CoMoCrB Compound CoWP CoWPB CoWB CoMoB CoMoCrBCobalt sulfate heptahydrate 18 g/L 18 g/L 9-28 g/L 3-26 g/L 3-26 g/LDimethylamine borane 0.6 g/L 0.8-6.0 g/L 0.6-6.0 g/L 0.6-6.0 g/LHypophosphorous acid 8 g/L 14 g/L Citric acid monohydrate 57 g/L 57 g/L42-84 g/L 28-84 g/L 28-84 g/L Pyrophosphoric acid  0-35.6 g/L 0-35.6 g/LTungsten (VI) oxide 6 g/L 17 g/L 4-17 g/L Molybdenum (VI) oxide0.01-0.45 g/L 0.01-0.45 g/L Chromium (III) chloride 0.001-5.0 g/Lhexahydrate Boric acid 24 g/L 16 g/L 0-31 g/L 0-31 g/L 0-31 g/L TMAH pHup to 9.4 pH up to 9.4 pH 9.0-9.5 pH = 8.8-9.5 pH = 8.8-9.5 Maleic acid0-1.5 g/L 0-1.5 g/L 0-1.5 g/L HEDTA 0-2.0 g/L 0-2.0 g/L 0-2.0 g/LTemperature 90° C. 90° C. >70° C. >65° C. >65° C. Surfactant PPG, RE-610PPG, RE-610 PPG, RE-610, PPG, RE-610, PPG, RE-610, Triton X-100 TritonX-100 Triton X-100 Deposition rate 15-20 nm/min 15-25 nm/min 20-200nm/min 20-250 nm/minPPG ≡poly-propylene glycolRE-610 ≡GAFAC RE-610, complex phosphate esters, manufactured by GAFCorp., New York, New YorkTriton X-100 ≡octylphenoxy polyethoxy ethanol, manufactured by Rohm andHaas, Philadelphia, Pa.

TABLE 2 Exemplary Compositions of Deposition Solutions and ChamberProcess Parameters used to form Films of CoWPB, CoWB, CoMoB, CoMoCrB andRu CoWPB CoWB CoMoB CoMoCrB Compound (high W) (high W) (high Mo) (highMo) Ru Cobalt sulfate heptahydrate 18 g/L 18 g/L 16 g/L 16 g/L Rutheniumnitroso chloride 2.36 g/L Dimethylamine borane 1.5 g/L 2 g/L 3.0 g/L 3.0g/L Hypophosphorous acid 7 ml/L Citric acid monohydrate 84 g/L 84 g/L 63g/L 63 g/L Tungsten(VI) oxide 17 g/L 17 g/L Molybdenum(VI) oxide 0.36g/L 0.36 g/L Chromium(III) chloride 1 g/L hexahydrate Boric acid 15.5g/L 15.5 g/L 15.5 g/L 15.5 g/L NH4OH 31 ml/L Hydroxylamine sulfate 0.75g/L Hydrazine sulfate 23 g/L Maleic acid 0.38 g/L 1.5 g/L 1.5 g/L HEDTA0.5 g/L 2.0 g/L 2.0 g/L EDTA 5 g/L Temperature 90° C. >80° C. >70°C. >70° C. >70° C. Surfactant PPG, RE-610 PPG, RE-610 PPG, RE-610 PPG,RE-610 Deposition rate 15-35 nm/min 20-70 nm/min 20-100 nm/min 20-100nm/min 20-40 nm/minPPG ≡poly-propylene glycolRE-610 ≡GAFAC RE-610, complex phosphate esters, manufactured by GAPCorp., New York, New York

Other noble catalytic metals, such as palladium (Pd) and rhodium (Rh) aswell as different combinations of the elements stated above for linerlayer 28 and cap layer 30 may additionally or alternatively be formed assub-film layers for a composite barrier layer formed from the methoddescribed in reference to FIG. 3. For example,cobalt-molybdenum-chromium (CoMoCr) may be formed as a sub-film layer ofa composite barrier layer. The solution composition for the formation ofa CoMoCr layer may include similar concentrations of components asdescribed for CoMoCrB without the inclusion of dimethlylamine borane. Assuch, the formation of a composite barrier layer described in referenceto FIG. 3 is not restricted to the alloys listed in Tables 1 and 2. Inaddition, the compounds listed in Tables 1 and 2 may be combined for theformation of the same composite barrier layer. In particular, a compoundlisted in Table 2 may be formed as a sub-film over a sub-film formedfrom a compound listed in Table 1 or vice versa. For example,cobalt-tungsten-phosphorus having a relative high concentration oftungsten (CoWP high W) listed in Table 2 may be formed over a sub-filmof CoWP listed in Table 1. In this manner, a composite barrier layerhaving a variation of tungsten may be formed. In yet other embodiments,any of the compounds listed in Tables 1 and/or 2 may be formed upon oneanother to form a composite barrier layer having a variation ofelemental concentration.

Although not necessarily limited thereto, maleic acid and/orhydroxyethyl ethylenediamine triacetic acid (HEDTA) have been found toserve as effective complexing agents for the deposition of filmsincluding cobalt. Moreover, the inclusion of pyrophosphoric acid hasbeen found to be advantageous for forming films including cobalt andmolybdenum. In contrast, the inclusion of ethylenediamine triacetic acid(EDTA) has been found to be beneficial as a complexing agent for thedeposition of films including ruthenium. Furthermore, the combination ofammonium hydroxide (NH₄OH), hydroxlamine sulfate, and hydrazine sulfatehas shown to be effective for depositing films including ruthenium. Itis noted that the values for such components as well as all othercomponent values listed in Tables 1 and 2 may be altered and still beused to produce sub-films for a composite barrier layer havingvariations of elemental concentrations. The values listed are merelyexemplary.

An alternative or additional method used to form a barrier layer havinga concentration variation of one or more elements involves an annealprocess which diffuses one or more elements to a particular region ofthe film to create additional interfaces with which to block a diffusionchannel. The anneal process may be conducted after the deposition of anylayer deposited by electroless plating techniques. In some embodiments,the anneal process may be performed subsequent to the method describedabove in reference to FIG. 3 to provide additional variation ofelemental compositions within a barrier layer. In other cases, theanneal process may be performed subsequent to the methods describedbelow in reference to FIGS. 5, 6 and 12. In yet other embodiments, theanneal process may be performed subsequent to a conventional electrolessdeposition process. In any case, the anneal method may be particularlyadvantageous for forming a barrier layer having phosphorus diffused nearthe middle of the film such that two additional interfaces are formedwith which to block a diffusion channel such as shown in FIGS. 2 c, forexample. The anneal process, however, may be configured to diffuse otherelements in addition or alternative to phosphorus. Furthermore, theanneal process may be configured to diffuse elements in regions of thesubstrate other than the middle.

A flowchart of an exemplary method which incorporates a diffusing annealprocess is shown in FIG. 4. In particular, FIG. 4 illustrates aflowchart including block 60 in which a bulk metallic film is formedupon a microelectronic topography using an electroless plating process.The term “bulk metallic film” may generally refer to a film having amajority concentration of metallic elements and, therefore, may refer toa barrier layer formed with a combination of any of the elementsmentioned above in reference to liner layer 28 and cap layer 30 ofFIG. 1. As noted in block 60 of FIG. 4, the bulk metallic film may beformed having a bottom portion, a top portion, and an intermediateportion interposed between the bottom and top portions. In someembodiments, one of the top and bottom portions may include a higherconcentration of at least one element than the intermediate portion andthe other of the top and bottom portions. Other variations of elementconcentrations, however, may be formed for the bulk metallic layer and,therefore, the method is not necessarily restricted to the arrangementof elements among the particular regions of the film recited in block 60of FIG. 4.

In some embodiments, the bulk metallic film may be formed upon and incontact with a metallic structure having a bulk elemental concentrationdifferent than the film, such as described for cap layer 30 in FIG. 1being arranged upon and in contact with metallization structure 22. Insuch cases, the bottom portion of the bulk metallic film may include ahigher concentration of at least one element than the intermediateportion and the top portion. In other embodiments, the bulk metallicfilm may be formed upon and in contact with a dielectric structure, suchas described for liner layer 28 in FIG. 1 being arranged in contact withdielectric layer 24. In such cases, the top portion of the bulk metallicfilm may include a higher concentration of at least one element than theintermediate portion and the bottom portion.

Following the formation of the bulk metallic film, the method continuesto block 62 as shown in FIG. 4. Block 62 includes annealing themicroelectronic topography to induce diffusion of at least one elementwithin the bulk metallic film such that the intermediate portioncomprises a higher concentration of the at least one element than thebottom and top portions. In general, the anneal process may includeexposing a bulk metallic film to a temperature between approximately400° C. and approximately 1000° C. for any predetermined length of time.A duration of at least approximately 10 minutes may be advantageous forensuring diffusion of a large percentage of the element to theintermediate portion of the bulk metallic film and, in some embodiments,the anneal process may be conducted for a time period up toapproximately 2 hours. In some embodiments, the heated environment towhich the bulk metallic film is exposed may include one or more elementshaving a propensity for diffusion into exposed portions of the bulkmetallic film, such as phosphorus or boron, for example. In some cases,the element included in the heated environment may be the same as one ofthe elements diffused into the intermediate portion of the bulk metallicfilm by the anneal process. In other embodiments, the element includedin the heated environment may not be one of the elements diffused intothe intermediate portion of the bulk metallic film by the annealprocess.

An alternative method for forming a barrier layer with a concentrationvariation of one or more elements is outlined in the flowchart shown inFIG. 5 and involves a balance of different deposition mechanismsactivated during a single deposition process. The different depositionmechanisms may be induced by an additive to the deposition solutionwhich slows the adsorption of one or more elements versus other elementsin the solution. The slower adsorption rate invokes a deposition processhaving different mechanisms of film growth which are dependent upon theconcentrations of different elements within the deposition solution. Asa result, although two elements may be deposited as a mixture within alayer, the concentration of the elements throughout the layer willdiffer. An exemplary agent which may be used to slow the adsorption ofone or more elements within a electroless plating solution may be but itnot necessarily limited to pyrophosphoric acid as shown above in Table 1for the formation of CoMoB and CoMoCrB.

The flowchart depicted in FIG. 5 includes block 66 noting the methodincludes exposing a microelectronic topography to a deposition solution.Such an exposure may include immersing the microelectronic topographywithin a bath of the deposition solution, dispensing the depositionsolution upon the microelectronic topography, or a combination thereof.In addition, the method includes block 68 in which a first sub-filmportion having a higher concentration of a first element than a seconddifferent element is formed by interfacial electroless reduction of thefirst element within the deposition solution until the second elementreaches a certain concentration within the deposition solution. Duringsuch a step, the first element within the deposition solution isdeposited at a faster rate than a second element by a mass-diffusioncontrol mechanism. At the point in which the second element reaches acertain concentration within the deposition solution, the depositionmechanism may change such that the second component is deposited as amajority by a self-assembly deposition mechanism. In particular, FIG. 5includes block 70 in which a second sub-film portion having a higherconcentration of the second element than the first element is formedupon and in contact within the first sub-film portion by chemicaladsorption. Such a deposition mechanism continues until the firstelement increases to a particular concentration within the depositionsolution. In response thereto, the deposition process reverts back tothe mass-diffusion control mechanism to deposit the first element as amajority within a third sub-film portion.

As shown in block 72 of FIG. 5, the deposition mechanisms may bereiterated to form a composite barrier layer having alternating regionsof relatively higher concentrations of the first and second elements,respectively. The reiteration of the deposition mechanisms may beautomatic by the inclusion of the aforementioned additive agent withinthe deposition solution and the fluctuation of elemental concentrationswithin the deposition solution. In this manner, the process is cyclicand is self-monitoring. It is noted that subsequent sub-film portionsmay have slightly different concentrations of the elements as comparedto the first and second sub-film portions, but may generally follow analternating sequence of having relatively greater concentrations of thedifferent elements.

In general, the deposition mechanisms may be reiterated any number oftimes and, therefore, any number of sub-films may be formed by thetechnique outlined in FIG. 5. In other embodiments, process may beterminated upon the formation of the first and second sub-film portionsand, therefore, block 72 may, in some embodiments, be omitted from themethod. It is noted that the formation of the first and second sub-filmsas described in blocks 68 and 70, and any subsequent sub-films may, insome embodiments, include the termination of dispensing the depositionsolution upon the microelectronic topography (if applicable) and/or thetermination of rotating the substrate holder as similarly describedabove in regard to blocks 43 a and 43 b of FIG. 3. Such a sequence ofsteps may advantageously allow sub-films to be formed havingsubstantially uniform elemental composition, uniform thickness, andsubstantially free of defects.

Barrier layer formation involving a balance of deposition mechanisms maybe particularly applicable for forming barrier layers with a variationof molybdenum. In particular, molybdenum may be particularly amenable toslow adsorption rates relative to other elements in the presence of anadditive agent, such as pyrophosphoric acid, for example. For instance,a barrier film including alternating regions of relatively higherconcentrations of cobalt and molybdenum, respectively, may be depositedusing the balanced deposition mechanism technique by having majoritycobalt portions formed by interfacial electroless reduction and majoritymolybdenum portions formed by a chemical adsorption. In addition,molybdenum oxide may be particularly suitable for formation from aprocess of balanced deposition mechanisms. Other elements withmolybdenum as well as other combinations of elements may also be formedas a barrier layer using the process of balanced deposition mechanismsand, therefore, the method is not necessarily limited to the fabricationof cobalt-molybdenum alloys or molybdenum oxide.

In addition or alternative to the methods described in reference toFIGS. 3-5, other methods for forming barrier layers having a variationof elemental concentrations may include controlling the process solutiontemperature on the substrate surface. More specifically, other methodsmay introduce a variation of solution temperature across a substrate toform a barrier film with a variation of elemental concentrations.Typically, the concentration of elements within an electrolesslydeposited film is dependent on the temperature at which the depositiontakes place. As such, introducing a variation of solution temperatureacross a substrate may induce a variation of elemental concentrations.One manner in which to control process solution temperature across asubstrate is shown and described in reference to FIGS. 6-10. Inparticular, FIGS. 6-10 illustrate a flowchart outlining a method tocontrol the flow pattern and, thus, the temperature variation of thesolution across the substrate surface, systems configured to implementthe method, and graphs outlining exemplary process parameters usedadminister the method. It is noted that the use of the methods andsystems described in reference to FIGS. 6-10 are not necessarilymutually exclusive to other methods for forming barrier layers with avariation of elemental concentrations. Rather, the methods and systemsmay, in some embodiments, be used in combination with any of the methodsdescribed in reference to FIGS. 3-5 to form a barrier layer.

As shown in the flowchart depicted in FIG. 6, the method may includeblock 76 in which a microelectronic topography is positioned within anelectroless plating chamber. The method further includes block 78 inwhich a deposition solution is dispensed at a plurality of locationsextending different distances from a center of the microelectronictopography each at a different moment in time during an electrolessplating process. In particular, when solution distribution in a firstzone is completed, the dispensing arm of the electroless depositionchamber moves to another position (not necessarily adjacent to the firstzone) and the solution is dispensed thereon. In addition to theplacement of dispensing the deposition solution, the amount, rate andduration the solution is dispensed on the microelectronic topography maybe controlled. Such a plurality of parameters may generally relate tothe flow pattern of the solution across the wafer. Consequently, themethod may include regulating a flow pattern of a solution to vary thetemperature of the solution across the microelectronic topography andinduce a variation of elemental concentrations within a deposited film.An exemplary system for controlling flow patterns of solutions across asubstrate is described in more detail below in reference to FIGS. 7 and8.

In addition to controlling the flow pattern of the deposition solution,the method may include altering the temperature of the dispensedsolution such that different regions of the substrate are exposed todifferent solution temperatures. In some embodiments, the exemplarysystem described in reference to FIGS. 7 and 8 may be configured todispense the solution at different temperatures across a substrate. Inaddition or alternatively, heating and/or cooling mechanisms within asubstrate holder of the electroless plating chamber may be used tochange the temperature of the deposition solution during plating. In anycase, solution temperatures for electroless plating operations maygenerally be regulated between approximately 20° C. and approximately120° C., or more specifically, between approximately 55° C. andapproximately 90° C. Warmer or cooler solution temperatures may be used,however, depending of the fabrication specifications of the process. Insome embodiments, the methods of controlling the process solutiontemperature and/or flow pattern across a substrate may induce ahorizontal variation of elemental concentrations. In addition oralternatively, the methods may be used to induce a vertical variation ofelemental concentrations. In particular, the method may include alteringthe flow pattern and/or temperature of the solution as the film isdeposited, such that elemental concentrations within the film varyacross regions of the microelectronic topography and/or vary with thethickness of the film.

Turning to FIG. 7, a top view of microelectronic topography 82 disposedwithin electroless plating chamber 80 is illustrated. As shown in FIG.7, electroless plating chamber 80 includes substrate holder 84 supportedby platen 86 and surrounded by chamber walls 88. The electroless platingchamber further includes dispensing arm 90 for supplying a depositionsolution onto microelectronic topography 82, which resides uponsubstrate holder 84. The cover of electroless plating chamber 80 is notshown in order to illustrate the alternate positions of dispensing arm90 relative to microelectronic topography 82. As shown by the dottedline outlines of dispensing arm 90 in FIG. 7, electroless platingchamber 80 may be configured to position dispensing arm 90 above aplurality of locations of microelectronic topography 82. Morespecifically, dispensing arm 90 may be connected to rotary drivemechanism 94 for positioning the suspended end of dispensing arm 90among positions 92 a-92 d with respect to fixed axis 96.

In this manner, electroless plating chamber 80 may be configured toposition dispensing arm 90 over a plurality of locations extendingdifferent distances from a center of microelectronic topography 82 eachat a different moment in time during an electroless plating process.More specifically, positions of dispensing arm 90 may be controlled fordelivering a deposition solution to a specific area of microelectronictopography 82. In embodiments in which substrate holder 84 is configuredto rotate microelectronic topography 82 during processing, such an arrayof different radial positions may advantageously offer full coverage ofthe microelectronic topography. In particular, solution dispensed fromdispense arm 90 may be distributed to cover different radial rings ofmicroelectronic topography 82, which collectively cover the entirety ofthe topography. Exemplary wafer rotation speed may be betweenapproximately 1 rpm and approximately 100 rpm and, in some embodiments,approximately 30 rpm, but faster or slower rotations speeds may be used.It is noted that the different areas of the microelectronic topographyupon which the solution is dispensed by dispense arm 90 may overlap toensure coverage of the entirety of the topography during processing, butgenerally the areas cover different regions of the topography and,therefore, are distinct.

Although FIG. 7 illustrates dispensing arm 90 positioned in fourdifferent locations, electroless plating chamber 80 may be configured toposition dispensing arm 90 at any number of different locations greateror less than four. In some cases, positioning dispensing arm 90 in ninedifferent positions has shown to provide sufficient coverage of adeposition solution over an entirety of a microelectronic topography,but the methods and systems described herein are not necessarily solimited. In addition, although positions 92 a-92 d are illustrated withrespect the same radial line of microelectronic topography 82, dispensearm 90 may be positioned along different radial lines of microelectronictopography 82. Furthermore, positions 92 a-92 d are not restricted tobeing evenly spaced with respect to each other. Rather, positions 92a-92 d may be spaced apart by different distances. Furthermore,dispensing arm 90 may be located at a position not overlyingmicroelectronic topography 82 in some embodiments, as shown by position92 d in FIG. 7. Although not necessary, such a position of dispense arm90 may be advantageous for loading microelectronic topography 82 in andout of electroless plating chamber 80. The program instructions used toregulate the distribution of solution from dispense arm 90 described inmore detail below may be configured to inhibit solution flow from thedispense arm in such a position.

In some embodiments, the positioning of dispense arm 90 may beprogrammed through a computer system coupled to or incorporated withinelectroless plating chamber 80. A schematic diagram of an exemplarycomputer system is illustrated in FIG. 8. As shown in FIG. 8, computersystem 100 includes processor 106 and storage medium 102, which in turnincludes program instructions 104. The storage medium may include anydevice for storing program instructions, such as a read-only memory, arandom access memory, a magnetic or optical disk, or a magnetic tape. Ingeneral, input 28 may be transmitted to processor 106, which may beconfigured to execute program instructions 104 within storage medium 102to provide output 109 to electroless plating chamber 80. In someembodiments, program instructions 104 may be configured to exclusivelyregulate the position of dispense arm 90. In other embodiments, programinstructions 104 may also include program instructions for regulatingother facets of electroless plating chamber 80, such as but not limitedto loading operations, drying operations, and pre-deposition orpost-deposition cleaning operations.

As shown in FIG. 7, dispense arm 90 may, in some embodiments, include aplurality of different sized nozzles 99. In such cases, programinstructions 104 may be configured to selectively dispense a depositionsolution through distinct sets of the plurality of different sizednozzles with respect to plurality of positions 92 a-92 c. Morespecifically, program instructions 104 may be configured to selectivelydispense a deposition solution through one or more of nozzles 99 at eachof positions 92 a-92 c. In some embodiments, the selected nozzles maydiffer among all of the positions. In other embodiments, the selectionof nozzles may differ for less than all of the positions. In any case,in light of the such adaptations of program instructions 104, block 78of the method described in reference to FIG. 6 may, in some embodiments,include dispensing the deposition solution through a first nozzle aboveone of the plurality of locations of the microelectronic topography andmay further include dispensing the deposition solution through a seconddifferent sized nozzle above another of the plurality of locations.

Since nozzles 100 are different sizes, different amounts of solution maybe deposited at different locations upon microelectronic topography 82.In addition, different size areas of microelectronic topography 82 maybe exposed to the deposition solution at a given time. In general, thediameters of nozzles 100 may be significantly smaller than a waferdiameter (e.g., between approximately ⅛ inch and approximately 1 inch,although other sizes may be used) such that only a portion of wafer isexposed to deposition solution thus creating an area with high densityof nucleation sites. In yet other embodiments, dispense arm 90 may notinclude a plurality of different sized nozzles and, therefore, such anadaptation may be omitted from the methods and systems described inreference to FIGS. 6-8.

In addition or alternative to selectively dispensing a depositionsolution through different sized nozzles, program instructions 104 maybe configured to vary the rate and/or duration at which a depositionsolution is dispensed. In this manner, the method, system and programinstructions described herein may be configured to vary the amount ofsolution dispensed upon microelectronic topography 82 in alternativemanners than described for varying the distribution of a solutionthrough different sized nozzles. For example, the method described abovein reference to FIG. 6 may, in some embodiments, include dispensing thedeposition solution at a first rate and/or duration above one theplurality of locations of the microelectronic topography and dispensingthe deposition solution at a second different rate and/or duration aboveanother of the plurality of locations of the microelectronic topography.In some embodiments, the selected rate and/or duration may differ amongall of the positions. In other embodiments, the selected rate and/orduration may differ for less than all of the positions. In general,deposition solution flow rate may vary between approximately 0.5 L/minand approximately 10.0 L/min and, more specifically betweenapproximately 2.0 L/min and approximately 3.0 L/min. Exemplary durationsof flow may generally be between 10 seconds and a few minutes and morespecifically between, approximately 30 seconds and approximately 60seconds, but longer or short durations may be employed. In addition,larger or smaller flow rates may be used.

In any case, the selected rates of flow may induce laminar flow of thedeposition solution in some embodiments. Laminar flow may beadvantageous in some cases, since it is less likely to cause bubbles onthe surface of microelectronic topography 82. The occurrence of bubblesupon a microelectronic topography during an electroless depositionprocess often causes undesirable random non-uniformity in depositionthickness. In other cases, however, the selected rates of flow mayinduce turbulent flow of the deposition solution. In some embodiments,program instructions 104 may be configured to pulse a depositionsolution through dispense arm 90 and, in some cases, pulse a depositionsolution at different frequencies with respect to different regions ofmicroelectronic topography 82. Furthermore, program instructions 104may, in some embodiments, be configured to vary the angle of the line oftrajectory from dispense arm 90 such that the solution is not limited tobeing dispensed perpendicular to the surface of microelectronictopography 82. Varying the angle of the solution trajectory may, in somecases, be particularly advantageous for filling narrow holes within atopography.

As shown in FIG. 7, dispense arm 90 may, in some embodiments, includethermocouple 98. In such embodiments, the method, system and programinstructions described in reference to FIGS. 6-8 may be configured todispense deposition solutions at different temperatures with respect tothe plurality of locations of dispense arm 90 during processing. Inparticular, the method described in reference to FIG. 6 may, in someembodiments, include dispensing the deposition solution upon one of theplurality of locations of the microelectronic topography at a firsttemperature and may further include dispensing the deposition solutionupon another of the plurality of locations of the microelectronictopography at a second distinct temperature. In this manner, the method,system and program instructions described in reference to FIGS. 6-8 mayintroduce solution temperature variation across a microelectronictopography in some embodiments. In particular, a thin layer of theprocess liquid on a substrate surface generally has low thermalcapacity, which allows the temperature of a solution to reduce quickly.Varying the timing at which the solution is distributed as well asvarying the temperature at which the solution is dispensed relative tosuch time-varying distribution may allow the solution temperature acrossthe microelectronic topography to be controlled either for a variationof temperature or temperature uniformity.

It is noted that in other embodiments the configuration of the method,system and program instructions to dispense a solution at varyingtemperatures with respect to different regions of a microelectronictopography may aid in introducing solution temperature uniformity acrossthe microelectronic topography. In particular, since a solution isdispensed at different locations and different times across a topographyusing the configurations described in reference to FIGS. 6-8, regions ofthe solution may evaporate at different times affecting the temperatureof the solution at such regions. The use of dispense arm 90 and programinstructions 104, however, may be optimized to account for suchfluctuations among regions of the solution to produce solutiontemperature uniformity across a microelectronic topography in someembodiments. For example, FIG. 9 illustrates the temperature of adeposition solution with respect to three zones of a microelectronictopography, each respectively corresponding to positions 92 a-92 c ofdispense arm 90. As shown in FIG. 9, the temperature of the solutionvaries at each of the zones due to dispensing the solution at differenttimes with respect to the zones. In particular, while the depositionprocess at zone 2 is active, the temperature of the solution at zone 1may drop according to E*H=F*T*S, where E=evaporation rate, H=heat ofevaporation, F=solution flow rate, T=solution temperature drop perangle/cycle and S=specific heat of the solution. Collectively, however,the variations of solution temperatures across the zones produce auniform average temperature across the microelectronic topography.

Although solution temperature uniformity may be contrary to theaforementioned objective of forming a film with a variation of elementalconcentration, the method, system and program instructions described inreference to FIGS. 6-8 are not necessarily limited to forming a filmwith a variation of elemental concentration. In particular, the method,system and program instructions may be used to form portions or anentirety of a barrier layer without variations of elementalconcentration. In yet other embodiments, one of the methods described inreference to FIGS. 3-5 may be used in combination with the method,system and program instructions described in reference to FIGS. 6-8 toinduce a variation of elemental concentration with a barrier layer whileincurring solution temperature uniformity across a microelectronictopography.

Consequently, program instructions 104 for positioning dispense arm 90may be configured to provide uniform or non-uniform heat density of thedeposition solution across microelectronic topography 82 by regulatingdispensing times across different positions. As a result, filmsdeposited using the method, system and program instructions described inreference to FIGS. 6-8 may formed with a uniform thickness profile orwith a varying thickness profile. As noted above, solution temperatureduring an electroless deposition process has a direct effect on thethickness uniformity of the resulting film. Since the method, system andprogram instructions discussed in reference to FIGS. 6-8 may beconfigured to induce variation or uniformity of solution temperatureacross a microelectronic topography, the method, system and programinstructions may be configured to induce variation or uniformity withregard to a thickness of a film deposited by electroless depositiontechniques.

Regardless of whether the method, systems and program instructionsdescribed in reference to FIGS. 6-8 induce solution temperatureuniformity or variation across a microelectronic topography, thetemperature fluctuations among the zones may change mechanism of filmgrowth from mass diffusion limited to reduction reaction rate limited,advantageously producing an amorphous (nanocrystalline) layer with lowdensity of pinholes or growth defects as well as lower minimum filmthickness and better surface roughness. Exemplary amorphous layersresulting from changes of film growth mechanisms during an electrolessplating process are shown in FIGS. 10 b and 10 c and are compared to alayer shown in FIG. 10 a formed from a conventional electroless platingprocess. In particular, FIG. 10 a illustrates a partial cross-sectionalview of an exemplary film deposited first by a reduction reaction ratelimited mechanism of film growth (denoted by relatively small granules110) and afterward by mass diffusion limited mechanism of film growth(denoted by relatively long and narrow upright granules 112). Such afilm structure is typical of conventional electroless plating techniquesin which a deposition solution is deposited continuously at one locationand at a single temperature throughout the deposition process.

FIG. 10 b illustrates an exemplary cross-section of a film depositedexclusively by a reduction reaction rate limited mechanism of filmgrowth (denoted by relatively small granules 114). Such film structuremay be formed in embodiments in which the temperature of the solutioncontinuously varies during the deposition of the film. FIG. 10 cillustrates an exemplary cross-section of a film deposited by mechanismsof film growth which switch between reduction reaction rate limited andmass diffusion limited (denoted by the mixture of relatively smallgranules 116 and relatively long and narrow upright granules 118). Sucha film structure may be formed in embodiments in which the temperatureof the solution varies at some periods and at other times issubstantially constant.

As shown in FIGS. 10 b and 10 c, films formed partially or wholly by areduction reaction rate limited mechanism of film growth includecomparatively less gaps than the film formed exclusively by a massdiffusion limited mechanism of film growth depicted in FIG. 10 a. As aresult, a film deposited by varying the solution temperature profileand/or solution flow rate may advantageously have less pin-holes andin-film growth defects. In addition, such films may be smoother. Inparticular, films formed partially or wholly by a reduction reactionrate limited mechanism of film growth may have a surface roughness ofapproximately 0.5 nm RMS, which is significantly smoother than filmshaving a surface roughness of approximately 2.0 RMS formed exclusivelyby a mass diffusion limited mechanism of film growth. Furthermore,smaller and fewer gaps within a deposited barrier layer may further aidin inhibiting diffusion of elements therethrough. More specifically, abarrier layer having smaller and few gaps may hinder diffusion ofelements from adjacent structures, such as described in reference toFIG. 1 for the configurations of liner layer 28 and cap layer 30adjacent to metallization structure 22. Moreover, smaller and fewer gapsmay inhibit hydrogen atoms from lodging with the deposited film,reducing occurrences of hydrogen outgassing during subsequent processingwhich may in turn affect the formation of features overlying the film.In addition, smaller and few gaps allow a denser film to be formed and,as a result, a thinner film may be deposited during a given processingtime as compared to films formed by conventional electroless depositionprocesses.

An exemplary set of dispensing times and sequence of positions for thedistribution of a deposition solution upon a microelectronic topographyis noted in Table 3. FIG. 11 illustrates a graph of the total processingtime versus zone location data taken from Table 3. As shown in Table 3and FIG. 11, an exemplary sequence of steps may extend across 9 zones ofa microelectronic topography with increasingly longer dispense timesprogrammed for Zone 1 thru Zone 9. Such a sequence and duration ofdispenses may be advantageous for negating the edge effect in someembodiments, such as in cases in which Zone 1 refers to the most centralzone on the microelectronic topography, Zone 9 refers to the edge mostzone on the microelectronic topography, and the other zones areinterposed therebetween. Films resulting from such a configuration mayhave substantially uniform thickness across the microelectronictopography or may have greater thicknesses near the edge of the wafer ascompared to near the center of the wafer.

As shown in Table 3, the steps may, in some embodiments, be segregatedinto distinct sets of steps. In particular, steps 1-11 may cycle througheach of the zones with a different sequence and dispensing times thansteps 12-20. In this manner, a method for depositing the film mayinclude dispensing the deposition solution in a first sequence of stepsamong the plurality of locations to form a first sub-film across asurface of the microelectronic topography. In addition, the method mayinclude dispensing the deposition solution in a second differentsequence of steps among the plurality of locations to form a secondsub-film across the microelectronic topography and upon the firstsub-film. Although the dispensing times and sequence of steps depictedin Table 3 may be advantageous for some configurations of amicroelectronic topography, the dispensing times and sequence of stepsmay vary from those depicted in Table 3. In particular, such a displayof data is merely exemplary. TABLE 3 Sequence of Dispensing Times (inseconds) per Zone of a Microelectronic Topography for an ElectrolessPlating Process Zone Zone Zone Zone Zone Zone Zone Zone Zone Step 1 2 34 5 6 7 8 9 1 8 2 6 3 3 4 1 5 1 6 1 7 1 8 3 9 10 5 11 8 12 1 13 1 14 115 2 16 1 17 3 18 3 19 6 20 5

An alternative method and system for controlling process solutiontemperature on a microelectronic topography are shown in FIG. 12 and 13.In particular, FIG. 12 depicts a flowchart of an exemplary method andFIG. 13 illustrates an exemplary system in which a gas is distributedover a plate disposed above a substrate holder configured for supportinga microelectronic topography. As will be described in more detail below,the method and system allows portions of a deposition solution in selectregions of the microelectronic topography to evaporate (i.e., removewater from the deposition solution) a faster rate than other regions,inducing solution temperature uniformity or variation across thetopography. In general, removing water from an electroless platingsolution will lower the temperature of the solution. In cases in which asolution temperature variation is induced, the evaporation of thesolution during processing may produce a horizontal variation ofelemental concentrations and, in some cases, a vertical variation ofelemental concentrations as well. In addition or alternative toevaporating select regions of the microelectronic topography, the gasmay be configured react with the surface of the microelectronictopography such that contaminants (i.e., debris and/or oxidized metal)may be removed from the surface topography. Furthermore, the gas may beadditionally or alternatively configured to regulate concentrations ofother gases within the electroless plating chamber.

As shown in block 120 of FIG. 12, the method may include exposing amicroelectronic topography arranged within an electroless platingchamber to a deposition solution. Such an exposure may include immersingthe microelectronic topography within a bath of the deposition solution,dispensing the deposition solution upon the microelectronic topography,or a combination thereof. An exemplary configuration of an electrolessplating chamber which may be used for the method depicted in FIG. 12 isillustrated in FIG. 13. In particular, electroless plating chamber 130includes substrate holder 132 upon which a microelectronic topographymay be supported. Suspended above substrate holder 132 is dispense arm134 and plate 136. In some embodiments, dispense arm 134 may include theconfigurations described in reference to FIGS. 6-8 and, therefore, maybe moveable to multiple positions above substrate holder 132. In otherembodiments, however, dispense arm 134 may be fixed. As such, theconfigurations of electroless plating chamber 130 of FIG. 13 andelectroless plating chamber 80 of FIG. 7 may be combined or may bemutually exclusive. In alternative embodiments, the method described inFIG. 12 may be used with an electroless plating chamber having a showerhead for dispensing a deposition solution. In other embodiments, themethod may be used with an electroless plating chamber which does notinclude solution dispense arm or shower head, but rather is configuredsuch that a microelectronic topography may be immersed within adeposition solution.

In any case, the deposition method may include block 122 as shown inFIG. 12 in which a gas is introduced into the electroless depositionchamber above a plate suspended above the microelectronic topography.Such a step may be performed within electroless plating chamber 130 byintroducing a gas into gas inlet 138 above plate 136. In someembodiments, electroless plating chamber 130 may further include outlet139 by which to remove the deposition solution and byproduct gases asshown in FIG. 13. In some cases, the gas introduced into electrolessplating chamber 130 may include nitrogen and, in some cases, may bespecifically the diatomic form of nitrogen (i.e., N₂). Such a gas may beparticularly applicable for increasing the evaporation rage of thedeposition. Other gases which may be applicable for increasing theevaporation rate of the deposition solution, however, may also oralternatively be used. In some embodiments, the gas may be configured tobe reactive with the surface of the microelectronic topography such thatcontaminants (i.e., debris and/or oxidized metal) may be removed fromthe surface topography. For instance, hydrogen gas or a fluorinatedcarbon gas at a substantially high temperature, such as greater than450° C., for example, may be introduced into the chamber to react withthe surface of the microelectronic topography. Furthermore, the gas maybe additionally or alternatively configured to regulate concentrationsof other gases within the electroless plating chamber.

It is noted that the sequence of steps associated with blocks 120 and122 is not necessarily limited to the order shown in FIG. 12. Inparticular, the step of introducing a gas into the electroless platingchamber may sometimes be initiated subsequent to the step of exposingthe microelectronic topography to a deposition solution, but the methodis not necessarily so restricted. In some case, the step of introducinga gas into the electroless plating chamber may alternatively beinitiated prior to the step of exposing the microelectronic topographyto a deposition solution. In other cases, the step of introducing a gasinto the electroless plating chamber may be initiated at substantiallythe same time as the step of exposing the microelectronic topography toa deposition solution.

In any case, the method in FIG. 12 continues to block 124 in which thegas is distributed to regions extending above one or more discreteportions of the microelectronic topography. In some embodiments, thedistribution of the gas to such regions may be used to invokeevaporation of the deposition solution at the one or more discreteportions of the microelectronic topography. For instance, the one ormore discrete portions may include the peripheral edge of themicroelectronic topography. In particular, gas introduced above plate136 may be directed to the outer edges of plate 136 down to theperipheral edges of the microelectronic topography. Such a route for thegas may be particularly advantageous for negating the edge effect insome embodiments. Films resulting from such a route may havesubstantially uniform thickness across the microelectronic topography ormay have greater thicknesses near the edge of the wafer as compared tonear the center of the wafer.

In some cases, plate 136 may be a disc having a diameter slightlysmaller than the microelectronic topography being processed. Forexample, plate 136 may have a diameter between approximately 150 mm andapproximately 190 mm for processing 200 mm microelectronic wafers.Alternatively, plate 136 may have a diameter between approximately 250mm and approximately 290 mm for processing 300 mm microelectronicwafers. Discs of larger or smaller diameters, however, may be used foreither sized wafer, depending on the fabrication specifications of theensuing device. In some cases, plate 136 may not be a disc and, thus,may be alternatively formed of a different shape including but notlimited to a square or a rectangle. Regardless of its shape, plate 136may, in some embodiments, include holes such that portions in additionor alternative to the peripheral edges of a microelectronic topographymay be exposed to the gas and, thus, have portions of a depositionsolution thereon evaporate at a faster rate than other portions of thetopography. The holes may be of any size and shape necessary forexposing a desired area of the microelectronic topography to the gasintroduced through gas inlet 138.

In some embodiments, the process of distributing the gas to regions ofthe microelectronic topography may include rotating plate 136. Suchrotation may advantageously direct gas to the edge and/or openingswithin plate 136 down to the microelectronic topography. In someembodiments, plate 136 maybe rotated in the same direction as substrateholder 132 as shown in FIG. 13. In other embodiments, plate 136 may berotated in the opposite direction as substrate holder 132. In eithercase, substrate holder 132 and plate 136 may be independently configuredto rotate clockwise and/or counterclockwise. An exemplary range ofrotation speed for plate 136 may be between approximately 100 rpm andapproximately 500 rpm, although faster or slower rates may be employed.In some embodiments, plate 136 and substrate holder 132 may be rotatedat the same speed. In other embodiments, however, plate 136 andsubstrate holder 132 may be rotated at different speeds. In either ofsuch cases, the rate of rotation of plate 136 may, in some embodiments,be optimized with respect to wafer rotation speed and solution flow ratein order to induce solution temperature variation or uniformity acrossthe microelectronic topography.

A plan view of a test wafer having a film with regions of differentelemental concentrations and thicknesses is shown in FIG. 14. Inparticular, a plan view of test wafer 140 is illustrated with multiplezones of different material thicknesses and elemental concentrationsdeposited using any of the methods and systems described above inreference to FIGS. 3-13. More specifically, FIG. 14 illustrates testwafer 140 with an electrolessly deposited film including annulus areas(denoted as zones 1-9), each having comparatively different thicknessesand comparatively different elemental concentrations. Zones 1-9 aregenerally formed separately and in any order. In some embodiments, zones1-9 may be formed by deposition of the annulus close to wafer edge,followed by deposition of a layer of another thickness within anadjacent annulus closer to wafer center, and so on. Although FIG. 14illustrates test wafer 140 having nine zones, the test wafer is notnecessarily so limited. In particular, test wafer 140 may include anyplurality of zones. In addition, test wafer 140 is not limited to havingzones 1-9 of substantially similar widths. As such, in some embodiments,zones 1-9 may be formed with different widths.

In some embodiments, zones 1-9 may be configured incrementally withrespect to their thicknesses as shown in the exemplary partialcross-sectional view of test wafer 140 in FIG. 15 a. In particular, zone1 may be configured to have the thinnest profile, zone 9 may include thethickest profile, and zones 2-8 may include incremental thicknessestherebetween. Exemplary thicknesses for the zones may be approximately100 nm at zone 9 of, approximately 30 nm at zone 1, thicknesses rangingfrom approximately 35 nm to approximately 95 nm at zones 2-8. Larger orsmaller thicknesses, however, may be employed for any or all of zones1-9, depending on the design specifications of the ensuing device. Asshown in another exemplary cross-sectional profile of test wafer 140 inFIG. 15 b, the thickness of zones 1-9 may not vary incrementally in someembodiments. Such a pattern layout is feasible since each zone is formedseparately and the thickness of each region is dependent on theselective distribution of the deposition solution. In such cases, thethicknesses of zones 1-9 may vary between approximately 30 nm andapproximately 100 nm, but larger or smaller thicknesses may be employed.Due to the methods and systems described herein, variations of elementalconcentrations may be incorporated into zones 1-9.

Similar to the variations of thicknesses, the variation of elementalconcentration may vary incrementally through zones 1-9 or may varyrandomly. Furthermore, the variation of elemental concentration may beindependent of the incremental alignment or randomness of thicknesseswithin the zones. As such, zones 1-9 in either of the configurations oftest wafer 140 illustrated in FIGS. 15 a and 15 b may include a randomvariation of elemental concentrations, an incrementally increasingconcentration of elements or an incrementally decreasing concentrationof elements. In any case, test wafer 140 may generally be used forcalibration of thin film metrology equipment such as acoustic wave,X-ray fluorescence, sheet resistance, RBS, and such. Conventionalmetrology calibrations typically utilize multiple test wafers. Aplurality of calibration wafers, however, is often costly due to thecosts for both the wafers themselves and for lost production time onmanufacturing tools due to qualification and calibration downtime. Asingle calibration wafer, such as test wafer 140, will allow significantcost advantages.

It will be appreciated to those skilled in the art having the benefit ofthis disclosure that this invention is believed to provide a system andmethods involving electroless plating processes for the formation ofmetallic layers and structures within microelectronic topographies.Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. For example, although the process chambers and methodsprovided herein are frequently described in reference to the depositionof barrier layers, the system and methods are not necessarily restrictedto such operations. In particular, the methods and systems describedherein may be used for the deposition of other types of layers and aswell as other operations such as but not limited to cleaning and dryingoperations. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims.

1. A microelectronic topography, comprising: a structure having a bulkconcentration of a first element disposed throughout the structure; anda film consisting essentially of one or more elements different than thefirst element formed in contact with the structure, wherein the film hasperiodic successions of regions each comprising: at least one regionwith a concentration of a second element greater than a set amount; andat least one region with a concentration of the second element less thanthe set amount.
 2. The microelectronic topography of claim 1, whereinthe periodic successions of regions comprise sub-layers verticallyarranged within the film.
 3. The microelectronic topography of claim 1,wherein the periodic successions of regions comprise regionshorizontally arranged within the film.
 4. The microelectronic topographyof claim 1, wherein the film is arranged upon the structure.
 5. Themicroelectronic topography of claim 1, wherein the film is arrangedbeneath the structure.
 6. The microelectronic topography of claim 1,wherein the first element comprises copper, and wherein the secondelement comprises cobalt.
 7. The microelectronic topography of claim 6,wherein a variation of the concentrations of cobalt among the periodicsuccessions of regions is between approximately 10% and approximately30%.
 8. The microelectronic topography of claim 1, wherein the secondelement comprises phosphorus, and wherein a variation of theconcentrations of phosphorus among the periodic successions of regionsis between approximately 3% and approximately 12%.
 9. Themicroelectronic topography of claim 1, wherein the second elementcomprises boron, and wherein a variation of the concentrations of boronamong the periodic successions of regions is between approximately 1%and approximately 2%.
 10. The microelectronic topography of claim 1,wherein the second element comprises molybdenum, and wherein a variationof the concentrations of molybdenum among the periodic successions ofregions is between approximately 1% and approximately 50%.
 11. Themicroelectronic topography of claim 1, wherein the second element isselected from a group consisting of hydrogen, tungsten, chromium,nickel, rhodium, ruthenium and palladium.
 12. The microelectronictopography of claim 1, wherein the one or more elements comprise cobalt,tungsten, and at least one of boron and phosphorus.
 13. Themicroelectronic topography of claim 1, wherein the one or more elementscomprise cobalt, molybdenum, and at least one of chromium and boron. 14.A microelectronic topography, comprising: a conductive structure havinga bulk concentration of copper disposed throughout the structure; and afilm formed in contact with the conductive structure comprisingalternating regions of comparatively greater and lesser concentrationsof cobalt.
 15. The microelectronic topography of claim 14, wherein thealternating regions further comprise comparatively greater and lesserconcentrations of one or more elements.
 16. The microelectronictopography of claim 14, wherein the one or more elements comprisemolybdenum.
 17. A method for processing a microelectronic topography,comprising: positioning the microelectronic topography within anelectroless plating chamber; dispensing a first deposition solution uponthe microelectronic topography to form a first sub-film within theelectroless plating chamber; removing the first deposition solution fromthe electroless plating chamber subsequent to the formation of the firstsub-film; and dispensing a second deposition solution upon themicroelectronic topography subsequent to the removal of the firstdeposition solution to form a second sub-film upon and in contact withthe first sub-film, wherein the second sub-film comprises multipleelements included within the first sub-film.
 18. The method of claim 17,wherein the second sub-film consists essentially of the same elements asincluded in the first sub-film.
 19. The method of claim 17, wherein aconcentration of at least one of the elements within the second sub-filmdiffers from a concentration of the same element within the firstsub-film.
 20. The method of claim 17, further comprising establishingchamber process parameters different than those used during theformation of the first sub-film prior to the step of dispensing thesecond deposition solution.
 21. The method of claim 20, wherein thefirst and second deposition solutions comprise substantially equalcompositions.
 22. The method of claim 17, wherein the first and seconddeposition solutions comprise substantially different compositions. 23.The method of claim 17, wherein at least one of the first and seconddeposition solutions comprises maleic acid and a component comprisingcobalt.
 24. The method of claim 17, wherein at least one of the firstand second deposition solutions comprises pyrophosphoric acid and acomponent comprising cobalt.
 25. The method of claim 17, wherein atleast one of the first and second deposition solutions comprisehydroxyethyl ethylenediamine triacetic acid and a component comprisingcobalt.
 26. The method of claim 17, wherein at least one of the firstand second deposition solutions comprise ammonium hydroxide and acomponent comprising ruthenium.
 27. The method of claim 17, furthercomprising terminating and subsequently resuming the step of dispensingthe first deposition solution during the formation of the firstsub-film.
 28. The method of claim 17, further comprising: rotating asubstrate holder upon which the microelectronic topography is positionedwithin the electroless plating chamber; and terminating and subsequentlyresuming the step of rotating the substrate holder during the formationof the first sub-film.
 29. The method of claim 17, further comprising:removing the second deposition solution from the electroless platingchamber subsequent to the formation of the second sub-film; andrepeating the steps of dispensing and removing the first depositionsolution subsequent to the removal of the second deposition solution toform a third sub-film upon and in contact with the second sub-film. 30.The method of claim 29, wherein a concentration of at least one of theelements within the third sub-film is closer to a concentration of thesame element within the first sub-film than a concentration of the sameelement within the second sub-film.
 31. The method of claim 29, furthercomprising establishing chamber process parameter settings differentthan those used during the formation of the first sub-film prior to thestep of repeating the steps of dispensing and removing the firstdeposition solution.
 32. The method of claim 17, further comprising:removing the second deposition solution from the electroless platingchamber subsequent to the formation of the second sub-film; andreiterating the steps of dispensing and removing the first depositionsolution and the steps of dispensing and removing the second depositionsolution subsequent to the formation of the second sub-film to formadditional sub-films above the second sub-film.
 33. The method of claim17, further comprising: removing the second deposition solution from theelectroless plating chamber subsequent to the formation of the secondsub-film; and consecutively dispensing and removing one or moreadditional deposition solutions different than the first and seconddeposition solutions subsequent to the removal of the second depositionsolution to form one or more additional sub-films above the secondsub-film.
 34. A method for processing a microelectronic topography,comprising: forming a bulk metallic film upon the microelectronictopography using an electroless plating process, wherein the bulkmetallic film comprises a bottom portion, a top portion, and anintermediate portion interposed between the bottom and top portions,wherein one of the top and bottom portions comprises a higherconcentration of a first element than the intermediate portion and theother of the top and bottom portions; and annealing the microelectronictopography to induce diffusion of the first element within the bulkmetallic film such that the intermediate portion comprises a higherconcentration of the first element than the bottom and top portions. 35.The method of claim 34, wherein the step of forming the bulk metallicfilm comprises forming the bulk metallic film upon and in contact with ametallic structure having a bulk elemental concentration different thanthe film, and wherein the bottom portion of the bulk metallic filmcomprises a higher concentration of the first element than theintermediate portion and the top portion prior to the step of annealingthe microelectronic topography.
 36. The method of claim 34, wherein thestep of forming the bulk metallic film comprises forming the bulkmetallic film upon and in contact with a dielectric structure, andwherein the top portion of the bulk metallic film comprises a higherconcentration of the first element than the intermediate portion and thebottom portion prior to the step of annealing the microelectronictopography.
 37. The method of claim 34, wherein the first elementcomprises phosphorus.
 38. The method of claim 34, wherein the step ofannealing the microelectronic topography further comprises diffusing oneor more other elements through the bulk metallic film such that theintermediate portion comprises a higher concentration of the one or moreelements than the bottom and top portions.
 39. The method of claim 34,wherein the step of annealing the microelectronic topography comprisesexposing the microelectronic topography to a heated environmentcomprising a second element different from the first element.
 40. Amethod for depositing a film upon a microelectronic topography,comprising: exposing the microelectronic topography to a depositionsolution; forming a first sub-film portion by interfacial electrolessreduction of a first element within the deposition solution until asecond different element reaches a certain concentration within thedeposition solution, wherein the first sub-film comprises a higherconcentration of the first element than the second element; forming asecond sub-film portion upon and in contact with the first sub-filmportion by chemical adsorption until the first element increases to aparticular concentration within the deposition solution, wherein thesecond sub-film comprises a higher concentration of the second elementthan the first element; and reiterating the steps of forming the firstand second sub-film portions to form a composite film comprisingconcentration variations of the first and second elements.
 41. Themethod of claim 40, wherein the first element is cobalt and the secondelement is molybdenum.
 42. The method of claim 40, wherein the firstelement is oxygen and the second element is molybdenum.
 43. The methodof claim 40, wherein the deposition solution comprises an agent to slowthe adsorption of the second element during the step of forming thesecond sub-film portion.